The present invention applies to a probe microscope such as a tunneling microscope or atomic force microscope for observing and measuring the shape of a micro area on a surface, local electronic state, or local nuclear state.
When physical property information such as electron spin, nuclear magnetic moment, and nuclear quadrupole moment is measured, it is very difficult conventionally to measure the two-dimensional or three-dimensional local distribution of, for example, impurities and defects in a semiconductor sample, even if the rate thereof in the whole is very low. The reason will be described hereunder. For example, in the case of electron spin resonance (ESR), the minimum number of spins N.sub.min which can be detected is expressed by the following equation. EQU N.sub.min =(.kappa.T/.mu..sup.2)(.DELTA.H/H.sub.o)(1/.pi..sup.2 Q.sub.o .eta..xi.)(.kappa.T.sub.d .DELTA.f/2P.sub.o).sup.1/2
where P.sub.o indicates the power of incident electromagnetic wave (V.sub.o.sup.2 /2R.sub.o), T.sub.d temperature of the detector, .DELTA.f a band width of the detection apparatus which is about 1 Hz to 10 kHz, Q.sub.o a constant representing the sharpness of resonance of the cavity resonator which is up to about 5000 at no load, .DELTA.H width of the adsorbed wave, H.sub.o intensity of the magnetic field, T power transmission factor from the oscillator to the cavity resonator, .kappa. a Boltzmann constant, .mu. magnetic moment of spin, .eta. a coefficient indicating the degree of effect of the magnetic behavior of the sample on the electromagnetic characteristics of the entire cavity resonator, and .xi. a coefficient derived from the cavity resonator which is between 1/3 and 1/8. When they are obtained by practical numerical values, the minimum number of spins which can be detected is at most 106 to 108 even in an ideal case. Therefore, it is quite difficult to analyze, for example, impurities and defects existing in a semiconductor sample or on the surface thereof on an atomic scale by this means.
Recently, on the other hand, a probe microscope using a micro probe as a detector such as a scanning tunneling microscope has be used widely as a means for structure observation and analysis of a sample surface on an atomic scale. Recently, a means for detecting the electron spin resonance phenomenon of a sample placed in a magnetic field by the micro probe of the aforementioned probe microscope has be proposed. This is indicated, for example, in Physical Review Letter, Vol. 62, No. 21, p. 2531 to 2534 and Japanese Patent Application Laid-Open No. 5-40100. The means detects ESR indirectly and has been proposed on the assumption that a tunneling current is changed at the same frequency by the magnetic moment which makes a precession motion at the Larmor frequency at the part of a sample where electron spin resonance occurs. It is indicated that the means separates and detects a tunneling current measured by the probe at each frequency by a filter.
According to the aforementioned prior art, the tunneling current which occurs in the gap between the sample in the electron spin resonance state and the tip of the micro probe contains the component which occurs on the basis of the sample surface shape and the high frequency component on the basis of the ESR. Namely, the tunneling current measured by the probe in this measurement contains different types of information such as the sample surface shape and electron spin resonance. Therefore, it is necessary to extract an ESR signal from the tunneling current and the ESR signal cannot be measured directly. As a result, to extract the ESR signal, it is necessary to repeat to scan the sample surface by the probe at each frequency of the electric field or magnetic field to be applied to the sample and to compare the frequency spectrum of the tunneling current which is obtained reproducibly at each frequency. Therefore, the extraction requires a lot of time and a complicated operation. In addition, the aforementioned measuring means can be applied only to a sample which generates a tunneling current, so that it is impossible to measure electron spin resonance of an insulating sample.